OS_MBUF_LEADINGSPACE

OS_MBUF_LEADINGSPACE(__om)

Macro used to get the amount of leading space in an mbuf (in bytes).

Arguments

Arguments	Description
__om	Pointer to mbuf (struct os_mbuf *)

Notes

This macro works on both normal mbufs and packet header mbufs. The amount of leading space is the number of bytes between the current om_data pointer of the mbuf and the start of the mbuf user data buffer.

Example

    uint8_t *dptr;
    uint16_t space;
    struct os_mbuf *om;
    struct my_data_struct my_data;

    /* Copy data from "my_data" into the start of an mbuf but only if there is enough room */
    space = OS_MBUF_LEADINGSPACE(om);
    if (space >= sizeof(struct my_data_struct)) {
        dptr = om->om_data - sizeof(struct my_data_struct);
        memcpy(dptr, &my_data, sizeof(struct my_data_struct));
    }